Liquid fuel injection pumps



A. J. ELLIS 3,435,770

LIQUID FUEL INJECTION PUMPS A ril 1, 1969 Filed May 9, 1967 @J/G. 22 M F/6.Zb 2i /4 FIG. 20 r, 22 /4 IIv 53 S F/G.5 //a Z V I 7 gal. 07% nrr'y United States Patent 3,435,770 LIQUID FUEL INJECTION PUMPS Arthur J. Ellis, 'Cheltenham, England, assignor to Bryce Berger Limited, Gloucestershire, England, a corporation of Great Britain Filed May 9, 1967, Ser. No. 637,208 Claims priority, application Great Britain, May 10, 1966, 20,632/66; Apr. 1, 1967, 18,152/67 Int. Cl. F04b 49/00 US. Cl. 103-41 7 Claims ABSTRACT OF THE DISCLOSURE A liquid fuel pump including a plunger which has a groove therein that defines a control edge for modifying the rate of pressure decay, said groove being less in depth at a point immediately adjacent the control edge than it is at a point remote from said edge.

This invention relates to liquid fuel injection pumps of the type for supplying fuel to the combustion chamber of an internal combustion engine through a conduit to a nozzle valve and comprising a plunger reciprocably mounted within a cylinder with means for imparting a constant stroke to the plunger, the plunger and cylinder bore defining a pumping chamber, at least one outlet from the pumping chamber, a delivery valve at said outlet, at least one port (formed in the' wall of the cylinder) and at least one complementary groove on the peripheral surface of the plunger including a longitudinally shaped control edge, the groove below the control edge being in continuous communication with the pumping chamber, the said control edge being generally helical in shape and arranged to register with the said port during a pumping stroke thereby to terminate the delivery of fuel from the pumping chamber by release of pressure from the pumping chamher, the resultant rate of pressure decay in the system being a function of several factors such as the minimum flow area at any point downstream of the pumping chamher, the dimensions and rate of closure of the delivery valve and the dimensions and rate of presentation of the control edge to the port and the relative dimensions of such port, the plunger being provided with means for rotational positioning about its longitudinal axis to adjust the timing of such pressure release, i.e. at what position of the plunger stroke such edge coacts with the port so that pressure release is initiated, and thereby to adjust the pump output for the stroke.

conventionally, for ease and simplicity of manufacture, these said ports are circular and Where used for re-filling the pump chamber as well as for adjustably timed release of pressure, it is generally accepted as advantageous to make such ports as large as practical. 0n the other hand, the larger the port, the more rapid will be the rate of pressure decay and it has recently been appreciated by the applicants that a too high rate of pressure decay can be a disadvantage. This is based on the evidence of engine combustion gas blow-back found at the nozzle valve, which blow-back is believed to be due to a condition when the rate of pressure decay in the system is greater than that required to permit closure of the nozzle valve and such that the system pressure at the nozzle valve becomes lower than the combustion gas pressure while the nozzle valve is still open.

The present invention is based on the aforesaid appreciation and upon the conception of new means for controlling the rate, as well as the timing, of pressure, decay without the same control limitations at present existing as regards shape and size of ports and the complementary groove or other escape means.

The object of the present invention is to provide im- "ice proved means for modifying the rate of pressure decay.

According to the invention, a liquid fuel pump of the kind referred to is characterised in that the cross section of the groove is such that its radial depth immediately adjacent to the control edge is less than its radial depth at another point more remote from such edge.

The pump aforesaid may be further characterised in that the control edge is formed on the plunger by a groove and rebate therein defining primary and secondary control edges; or further characterised in that the said two edges are parallel to each other; or further characterised in that the radial depth of the rebate adjacent to the primary control edge increases progressively towards or away from such edge; or further characterised in that the primary and secondary control edges are not parallel to each other.

As shown in the accompanying drawings,

FIG. 1 is a longitudinal section of one example of the invention;

FIGS. 2a, 2b, 2c and 2d are fragmentary cross-section on line A-A of FIG. 1;

FIGS. 3 and 4 are side elevations showing the upper ends of alternative forms of plunger,

FIG. 5 is a part longitudinal section of a cylinder and plunger of alternative form providing hydraulic pressure balance about the plunger.

As shown in the drawings, FIG. 1 shows a pump cylinder 10, with diametrically opposed ports 17, a pump plunger 11 located therein, a delivery valve 12, and conduit 16, with the usual control edge 13 formed on the plunger by a helical groove 14, in continuous communication with the space above the plunger via a longitudinal groove 15, the control edge being shown in a modified form in accordance with the invention and parallel to the helical groove. The pump plunger is constructed at its outer end in conventional manner with a head 11a complementary to an actuating cam (not shown) and with a toothed segment 11b complementary to a toothed control rack (not shown). Conventional spring return gears (not shown) is provided for the plunger.

The shape of the modified form may be in accordance with the cross-sections in FIG. 2(a) as a constant depth rebate providing substantially two defined edges 18 and 19 respectively primary and secondary edges. Another alternate form is shown in FIG. 2( b) as a sloping rebate of greatest depth adjacent to the primary control edge 21; or FIG. 2(0) as a sloping rebate of least depth adjacent to the primary control edge 22; or 2(d) as a rebate of progressively varying depth of least depth adjacent to the primary control edge 23. FIG. 3 shows a pump plunger in accordance with the invention having a rebate at the primary control edge of any of the forms shown in FIG. 2 and of progressively increasing width in the longitudinal direction of the plunger with greatest width at that end of the primary control edge determining the largest pump delivery stroke. FIG. 4 shows a pump plunger similarly in accordance with the invention and with a rebate of progressively decreasing width having its least width at that end of the control edge determining the largest pump delivery stroke.

For reasons of hydraulic pressure balance about the plunger, two or more escape means may be provided around the periphery of the plunger, each with a control edge coacting simultaneously with separate ports in the cylinder. The modifications herein described may be incorporated at any one or all of these control edges and provided that at least two such escape means are provided, one of said escape means may be of a conventional radial depth, the other being of the modified radial depth and position in accordance with the invention and not acting simultaneously with the other escape means and their coacting ports but still giving an effective degree of hydraulic balance. An example of this is as shown in the drawing 3 FIG. 5, the cylinder 50 having two diametrically opposed ports 52, and the plunger 51, having one control edge 53, provided by an escape groove of conventional radial depth and position, the other control edge 54 being provided by a second escape groove having its radial depth and position in accordance with the invention.

The invention is not restricted to the above details. For example, the longitudinal groove referred to in the above description may be replaced by a relieved area, or spill passage, or a drilled hole while the converse construction is also included, i.e. the control edge or edges could be formed in the cylinder and the complementary port or ports in the plunger. Also the relative rotational adjustment could also be applied to the cylinder instead of, or in addition to, such movement of the plunger and in that case the two adjustments could be efiected as a function of different factors.

In a specific example, a pump generally in accordance with the illustration FIG. 1, operating at 214 strokes per min. having a plunger stroke of 22 mm. and plunger diameter 24 mm., a delivery valve of 250 cubic mm. unloading volume, delivering 3750 cubic mm. of liquid fuel at a peak pressure of approximately 650 kgm./sq. cm. having two ports 6 mm. diameter in the cylinder coacting with two conventional helical escape grooves in the plunger periphery each being 2.5 mm. deep and 6.35 mm. Wide in a plane normal to the control edge formed by each groove, one control edge being modified in accordance with the invention as illustrated by FIG. 2a, the rebate formed being 0.25 mm. deep and 2.22 mm. wide in a plane normal to the primary control edge thus formed. Such proportions were found to be effective to eliminate or sustantially reduce gas blow-back at a nozzle valve having a theoretical valve closure time of 0.57 millisecond.

What I claim is:

1. A liquid fuel injection pump comprising a cylinder, a plunger reciprocably mounted therein, defining a pumping chamber at one end thereof, means for imparting reciprocation at a constant stroke to said plunger, at least one delivery outlet from said chamber, a delivery -valve at said outlet, at least one port and complementary groove defining a control edge at the inner surface of the cylinder and periphery of the plunger in continuous communication with the pumping chamber, the said control edge being generally helical in shape, means for effecting relative rotational positioning of the plunger and cylinder to adjust the timing of relative register in the reciprocal movement of the plunger to adjust the pump output for each stroke, characterised in that the cross section of the groove is such that its radial depth immediately adjacent to the control edge is less than its radial depth at another point more remote from such edge.

2. A liquid fuel injection pump according to claim 1 further characterised in that the control edge is formed on the plunger by a groove and rebate therein defining primary and secondary control edges.

3. A liquid fuel injection pump according to claim 2 further characterised in that the said two edges are parallel.

4. A liquid fuel injection pump according to claim 2. further characterised in that the radial depth of the rebate decreases progressively away from the primary control edge up to the secondary edge.

5. A liquid fuel injection pump according to claim 2 further characterised in that the radial depth of the rebate adjacent to the primary control edge increases progressively away from the primary control edge up to the secondary edge.

6. A liquid fuel injection pump according to claim 2 further characterised in that the primary and secondary control edges are parallel to each other.

7. A liquid fuel injection pump according to claim 2 further characterised in that the primary and secondary control edges are not parallel to each other.

References Cited UNITED STATES PATENTS 2,211,252 8/ 1940 Bremser.

2,348,282 5/ 1944 Bremser.

2,612,842 10/ 1952 Steven et a1 103-41 2,696,786 12/1954 Fleck et al 103-41 2,740,667 4/ 1956 Dickson et al.

2,890,657 6/1959 May et al l03l54 X 3,123,006 3/1964 Partridge l03-l54 X 3,368,491 2/ 1968 Shook et al.

HENRY F. RADUAZO, Primary Examiner.

WARREN J. KRAUSS, Assistant Examiner.

US. Cl. X.R. 1032, 157 

